Isidore was an ethnic Greek born in Thessaloniki during the latter part of the 1290s where he became a teacher and spiritual guide.
Career
As a disciple of Pope Gregory I, he was drawn into the dispute between the followers of Gregory Palamas and Barlaam of Seminara over Hesychasm during the middle decades of the fourteenth century.
During the two and a half years of his patriarchate, Isidore I sought to have the whole Byzantine Church accept the Palamite dogmas. He selected bishops only from the Palamite party. He instituted harsh penalties for those who refused to submit.[2][bettersourceneeded]